An intelligent temperature transducer (smart sensor) has a built-in transducer electronic data sheet (TEDS) to make the measurement conversion and provide the data in units of temperature to the network controller which may contains processors. To do this, the smart sensor module also contains the digital interface to provide a communication channel between the network control and the smart sensor.
There are two main components of a functional smart sensor:
1) a transducer interface module (TIM) and
2) a network capable application processor (NCAP)
TIM
A TIM contains the interface, signal conditioning, Analog-to-Digital and/or Digital-to-Analog conversion and in many cases, it also contains the transducer. A TIM can range in complexity from a single sensor or actuator to many transducers including both sensors and actuators.
NCAP
An NCAP is the hardware and software that provides the gateway function between the TIMs and the user network or host processor (the transducer channel).
A transducer channel is considered 'smart' because of three features:
- It is described by a machine-readable, Transducer Electronic Data Sheet (TEDS).
- The control and data associated with the transducer channel are digital.
- Triggering, status, and control are provided to support the proper functioning of the transducer channel.
An NCAP or a host processor, controls a TIM by means of a dedicated digital interface medium. The NCAP mediates between the TIM and a user defined digital network. The NCAP may also provide local intelligence.
In brief, the smart sensors can perform there tasks in following sequence.
Self calibration:
Self-calibration means to adjust the deviation of the output of sensor from the desired value when the input is at minimum or it can be an initial adjustment of gain. Calibration is needed because their adjustments usually change with time that needs the device to be removed and recalibrated. If it is difficult to recalibrate the units once they are in service, the manufacturer over-designs, which ensure that device, will operate within specification during its service life. These problems are solved by smart sensor as it has built in microprocessor that has the correction functions in its memory.
Computation:
Computation also allows one to obtain the average, variance and standard deviation for the set of measurements. This can easily be done using smart sensor. Computational ability allows to compensate for the environmental changes such as temperature and also to correct for changes in offset and gain
Communication:
Communication is the means of exchanging or conveying information, which can be easily accomplished by smart sensor. This is very helpful as sensor can broadcast information about its own status and measurement uncertainty.
Multisensing:
Some smart sensor also has ability to measure more than one physical or chemical variable simultaneously. A single smart sensor can measure pressure, temperature, humidity gas flow etc.
From the definition of smart sensor it seems that it is similar to a data acquisition system, the only difference being the presence of complete system on a single silicon chip.